I've read that you're not supposed to put live rock into a QT bc it will absorb the medication. When I set mine up, I just used PVC elbows for the fish to hide.
I usually replaced about 3 gallons every 2 to 3 days. I checked ammonia daily and really didn't have issues. The ammonia badge is great to use though. After about a month of the tank running (I ended up having them in QT for 2 months), the tank cycled and the QT care was easy. Water changes were done more so to lower the nitrate level than any other issue. And yes some say that its not possible for the nitrate level to climb high enough to cause an issue, but the fish (1 clown, 2 yellow-tail blue damsels, and one royal gramma) were visibly distressed and responded much better when the nitrate levels dropped.
From what I've read, if you are going to treat, no carbon since that will just pull it out. I used an hang over the back filter stuffed with filter floss to just collect the particulate matter. The trick was making sure the fish ate ALL of the food added, and if any is missed, just scoop out with the net so that it doesn't add to the build up of ammonia. For medication, I'd get Prazipro (for internal parasites) and some form of copper (I used Coppersafe but many use Cupramine) for ich and gill flukes. If you use Coppersafe, the only copper test that will work is the API which tests for total copper. If you get cupramine, than the salifert copper test will work. Of course testing for copper is required because of how toxic it is. You may already know all this or have a lot of experience but I figured I'd just add some details since I just went though this QT business over the summer.
And for lights, I didn't really pay much attention to that. the fish were kept in the kitchen (on the Island) so if they wanted somewhere dark to go they had the PVC elbows, one for each fish so no fighting.